Allergy Blood Test Vs Allergy Skin Test: Whats The Difference
Allergy blood tests and allergy skin tests are two of the most common forms of allergy testing. During an allergy skin test, your healthcare provider creates tiny pinpricks in your skin and then applies an allergen to check for a reaction.
Skin tests deliver immediate results, but blood tests take a few days. Skin tests tend to be more accurate, but some people cant have allergy skin tests. If you have a skin condition such as hives or a rash, or youre taking antihistamines, allergy skin tests wont deliver reliable results. In these cases, you may need an allergy blood test.
Why Allergy Testing Is Performed
Allergies affect more than 50 million people living in the United States, according to the American College of Allergy, Asthma, and Immunology . Inhaled allergens are by far the most common type.
The World Allergy Organization estimates that asthma is responsible for 250,000 deaths annually. These deaths can be avoided with proper allergy care, as asthma is considered an allergic disease process.
Allergy testing can determine which particular pollens, molds, or other substances youre allergic to. You may need medication to treat your allergies. Alternatively, you can try to avoid your allergy triggers.
How A Skin Prick Test Is Done
A nurse will explain the test to you and your child.
HH-III-74 1/88, Revised 10/18 | Copyright 1988, Nationwide Children’s Hospital
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What Happens If I Have An Allergy
Depending on the allergy, your healthcare provider may recommend one or more of these steps:
- Minimize exposure to allergens: Avoid ones that cause severe reactions, such as latex or certain foods.
- Take daily allergy medications: Antihistamines can prevent or reduce allergic rhinitis and other symptoms.
- Get allergy shots: This type of immunotherapy can decrease the immune systems response to certain allergens like pet dander. You should get allergy shots for three to five years to experience maximum benefit. Allergy shots can be costly, but they often provide long-lasting relief, even after the shot series is completed.
- Have a medical alert card: A card or medical alert jewelry lets others know about your severe allergy. It tells them you could have an anaphylactic response to peanuts, bee stings or other allergens.
- Carry an epinephrine injection: Keep this medicine with you at all times if youre at risk for an anaphylactic allergic reaction.
A note from Cleveland Clinic
Allergic reactions can range from annoying congestion to life-threatening anaphylactic shock. Allergy tests can identify substances that cause these types of allergic reactions. There are different allergy tests. Your healthcare provider will choose the best test for you based on symptoms and potential allergy triggers. If you have allergies, you can take steps to get symptom relief.
Types Of Allergy Testing:
Our allergists diagnose allergies in children with the combination of an allergy skin test or scratch test and patient medical history. Allergy skin testing involves a simple series of tiny scratches on the back using a small instrument similar to a small plastic toothpick. Each toothpick contains trace amounts of an allergen. We test for a variety of environmental allergens such as tree, weed, and grass pollen, as well as, pet dander and molds. If you have a specific allergen you would like to be tested for, please let our offices know when scheduling. After a nurse administers the test, reactions may take 15-20 minutes to appear. Typical reactions are mild and will cause a small, itchy bump like a mosquito bite.
An allergist reviews the reactions and determines if additional testing is needed. In these cases, intradermal testing may need to be done on the forearm to provide more detailed results. During these tests, a small amount of the allergen is injected under the skin of the arm to see if it causes a reaction.
Another option is a blood test. This requires a simple blood draw that is sent off to the lab to determine if IgE levels suggest an allergy. A blood test can be used if a patient is already on antihistamines but is less accurate than skin test when diagnosing allergies.
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In This Article You Will Find Information About
Hallmark allergy symptomsassociated with allergic rhinitis and other allergies like food-borne onessuch as itchy eyes, a runny nose, and hives, as well as sneezing, coughing, or a scratchy throat, are the result of your bodys immune system attacking what it perceives as a foreign substance. Allergies are the sixth leading cause of chronic illness in Americansand one of the most common health issues among kids.1 Despite their prevalence, allergies are often overlooked, with many people choosing to just power through them rather than get proper treatment. But trying your best to ignore your allergies isnt advisable. Left unchecked, allergies can be more than just an annoyance. They can negatively impact your quality of life.
Instead, book an appointment with your doctor or an allergist. Theyll be able to determine the source of your allergy, and develop a customized plan to help get you some relief. Then, read on to discover what you should know before allergy testing, like the different types of diagnostics, how to prepare for an allergy test, and things you should and shouldnt do. That way, therell be minimal surprises and youll know what to expect at an allergy test.
Medications To Stop Before Allergy Testing
WHY DO I NEED TO STOP SOME MEDICATIONS BEFORE AN ALLERGY TEST?
- When you are allergic to a substance, your body releases certain chemicals such as histamine. When these chemicals are released in the skin during a test, we see a small bump in the skin that is often surrounded by redness. Certain medications can decrease this response and cause allergy testing to look negative even if you do have allergies.
- Other medications can be dangerous to take if you are having an allergy test. Some medications can increase your chance of a life-threatening reaction to an allergy test or make treating a severe reaction more difficult.
- You only need to consider stopping medications if you are going to have a skin test for allergies. If your allergy test will be done with a blood draw from the vein no medications need to be stopped.
- It is important to review your list of medications with your ENT allergist in order to ensure the most accurate and safe outcome when you have your test.
WHAT MEDICATIONS DO I NEED TO STOP BEFORE AN ALLERGY TEST?
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The Risks Of Allergy Testing
Allergy tests may result in mild itching, redness, and swelling of the skin. Sometimes, small bumps called wheals appear on the skin.
These symptoms often clear up within hours but may last for a few days. Mild topical steroid creams can alleviate these symptoms.
On rare occasions, allergy tests produce an immediate, severe allergic reaction that requires medical attention. Thats why allergy tests should be conducted in a doctors office that has adequate medications and equipment, including epinephrine to treat anaphylaxis, which is a potentially life threatening acute allergic reaction.
Call 911 immediately if you have symptoms of anaphylaxis, such as:
- swelling of the throat
How Do You Read Allergy Test Results
Only your doctor or allergist can accurately read the results of your allergy test. However, keep in mind that skin tests will show visible results, and blood tests will show higher than normal levels of IgE antibodies. And, youll definitely notice if you have a reaction to ingesting a food that youre allergic to during a challenge test. After that, your provider will come up with a treatment plan specifically for the type and severity of allergy you have. Be sure to ask them any questions you may have and keep an open line of communication to update them on your progress and any other reactions you may experience.
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Skin Prick Or Scratch Test
One of the most common allergy tests is the skin prick test for allergens, which commonly checks for allergies to airborne particles like pollen and animal dander. First, your doctor or allergist will prick the skin on your back or forearm with a thin needle, or theyll scratch it with a sterile device to lightly puncture it. Theyll then expose it to anywhere from 10 to 50 potential allergens, depending on which ones they suspect, to see what you might have a reaction to. It usually takes about 15 minutes and, if you have an allergy to one or more of the substances, your skin will become red, with a possible rash or raised spots known as wheals.
What You Can Do Before An Allergy Test
Just because youre preparing for an allergy test, that doesn’t mean you should be discouraged from living life to the fullest. Always check with your doctor or allergist to confirm what you definitely should avoid, but, otherwise, you can usually go about your daily business. And, rest assured, you can still continue with some of these things people wonder about before allergy testing.
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What To Check In Advance
Leading up to that first visit, speak to your doctor or allergist to ensure that you are not taking any medications that could cause problems at your appointment.
Some types of medications interfere with skin-prick testing, especially antihistamines, says Dr. David Stukus, a pediatric allergist and director of the food allergy center at Nationwide Childrens Hospital in Ohio. You may be asked to stop using these medications for around five days before seeing the allergist to prepare for testing.
Stukus stresses, however, that its important to ask your health-care provider before discontinuing any medications. For instance, medicines such as asthma inhalers, should not be stopped.
What Other Tests Are Available For Allergy Testing
Skin prick or scratch tests, intradermal tests, patch tests, and oral food challenges are usually performed by an allergist or dermatologist. These tests can be subjective and depend on factors such as dose of allergens, administration of the tests, and interpretation of results.
Your healthcare provider may also try eliminating foods from your diet and then reintroducing them to find out what you are allergic to. It is important that these tests be done under close medical supervision, as a life-threatening anaphylactic reaction is possible.
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Immunoglobulin E Blood Test
As the name implies, for this one, a sample of your blood will be sent to a lab and mixed with potential allergens. There, the level of IgE antibodieswhich are produced during an allergic reactionwill be checked. Though it seems like this might be the most accurate way to diagnose an allergy, IgE blood tests actually have a higher rate of false-positivesthats why theyre not usually the initial go-to.
My Allergy Test Was Negative But I Continue To Have Symptoms What Else Could It Be
You could have an allergy-like condition that is not mediated by IgE for which there are no specific laboratory tests. You might have a genetic hypersensitivity problem, such as sensitivity to gluten with celiac disease or have an enzyme deficiency, such as a lactase deficiency causing lactose intolerance. It could also be another disease that is causing allergy-like symptoms. It is important to investigate your individual situation with your healthcare provider’s assistance. Test results alone cannot diagnose allergies, but rather confirm a diagnosis when circumstances suggest an allergy is likely. Results from any type of allergy test have to be interpreted along with your medical history by a healthcare practitioner who is trained to diagnose allergies specifically.
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Preparing For Skin Testing
Prescription and non-prescription antihistamine medications interfere with skin testing. Please review the list of commonly used allergy, cough and cold medications below and make sure these are discontinued before your skin testing visit.
Continue other daily medications including: asthma inhalers, montelukast , and nasal steroids .
If you are unable to stop antihistamines because of the severity of your symptoms, please keep your appointment. Another approach to testing will be considered by your provider.
If you are not certain whether the medication you are taking is an antihistamine, are concerned about discontinuing your medications, or if you have any other questions, please contact the UCSF Allergy/Immunology Clinic at 353-2725.
Oral Antihistamines
- Brompheniramine
- Chlorpheniramine
- Loratadine (Alavert, Claritin, Claritin-D, Claritin Rev
Nasal Sprays
- Azelastine HCL Nasal Spray
- Dymista Nasal Spray
- Olopatadine HCL Nasal Spray
Other Medications
UCSF Health medical specialists have reviewed this information. It is for educational purposes only and is not intended to replace the advice of your doctor or other health care provider. We encourage you to discuss any questions or concerns you may have with your provider.
How To Prepare For Your Allergy Test
As you embark on your allergy testing, there areseveral important things to remember. Your testing process may take 60-90 minutes but will result ininformation on which allergens you react to and how severely you react to eachone. Be sure and inform your physicianand staff if you are not feeling well or have started taking any newmedications or have developed any new medical problems prior to the testing.
The testing will involve needle pricks, usuallydone on the upper arm. Wear comfortable clothing that allows for easy exposureof this area. It is best to avoid tightor restrictive clothing. You may alsohave vital signs and breathing tests administered during this process.
Leave the lotions at home. Identifying your allergic responses dependson a reaction between the inflammatory cells in the skin and the antigens. In order to insure accurate test results, itsbest to avoid lotions or skin treatments that could interfere with the testingresults.
No strenuous physical activity immediately beforethe test. Vigorous physical exercisecould potentially increase the risk of an allergic reaction during thetesting. Its best to delay exerciseuntil at least 3 hours after your testing.
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When You Need Them And When You Dont
Allergy tests may help find allergies to things you eat, touch, or breathe in. They are usually skin or blood tests.
However, allergy tests alone are generally not enough. It is important to have a doctors exam and medical history first to help diagnose allergies. If the exam and medical history point to allergies, allergy tests may help find what you are allergic to. But if you dont have symptoms and you havent had a medical exam that points to an allergy, you should think twice about allergy testing. Heres why:
What Do Allergy Blood Test Results Mean
Everyone has some IgE in their blood, but elevated levels may indicate an allergy. Different labs use different brands of allergy blood tests, so the scoring system for results can vary from brand to brand. Allergy blood tests dont indicate the severity of an allergy. So if you do have an allergy, talk to your doctor about the risk of anaphylaxis. You may need to carry an emergency epinephrine injection with you at all times.
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Unreliable Test Results Can Lead To Unnecessary Changes In Your Lifestyle
If the test says you are allergic to some foods, such as wheat, soy, eggs, or milk, you may stop eating those foods. You may end up with a poor diet, unnecessary worries and frustration, or extra food costs. If the test says you are allergic to cats or dogs, you may give up a loved pet.
And tests for chronic hivesred, itchy, raised areas of the skin that last for more than six weekscan show something that may not look normal but is not a problem. However, this can lead to anxiety, more tests, and referrals to specialists.
How Do I Know If I Need An Allergy Test
If youre allergic to allergens in the air like dust, pollen or pet dander, you may develop allergic rhinitis. Also known as hay fever, this allergic reaction causes:
Food allergy symptoms typically occur within 30 minutes of food ingestion but may occur up to two hours after ingestion. People with food allergies may experience:
- Skin symptoms such as hives, swelling of the face, lips or tongue, generalized itching.
- Respiratory symptoms such as coughing, wheezing, shortness of breath, chest or throat tightness.
- GI symptoms such as nausea and vomiting, abdominal pain and cramps, vomiting and diarrhea.
- Cardiovascular symptoms such as pale skin, weak pulse, dizziness or lightheadedness.
People who are allergic to latex, fragrances or metals like nickel may develop contact dermatitis. This allergic reaction affects your skin. You may have:
- Burning sensation on skin or blisters.
- Skin rash or itchy skin.
A patch test, performed by a dermatologist, is used to diagnose these types of reactions.
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